Ultraviolet radiation systems are known for the treatment of water. In one type of system an ultraviolet bulb or tube is mounted in a housing which is transparent to ultraviolet radiation. This is surrounded by a vertically oriented annular chamber containing water to be treated. In some embodiments the ultraviolet radiation is used to generate ozone to sterilise the water. In other embodiments the ultraviolet radiation provides the sterilisation directly. Representative patents of such technology are U.S. Pat. No. 4,141,830; US 4,273,660; US 6,099,799 and US 6,193,894.
It is also known from U.S. Pat. No. 6,015,229 to disinfect fluid by passing fluid flow through a uniform array of ultraviolet lamps having cross-sections perpendicular to the direction of fluid flow. Flow defecting delta wings are positioned to create pairs of vortices that either rotate in the same direction or in directions opposed to one another to assist in mixing the fluids while exposing them to ultraviolet radiation.
In U.S. Pat. No. 5,994,704 there is also described a flowthrough photochemical reactor using ultraviolet radiation. Deflectors are imposed in the flow path to create a turbulent flow to increase the uniformity of the fluid's exposure to photons radiating from a source within a tube. The flow path is substantially annular to that central source.
It would be desirable to provide a system to kill or inhibit growth of microorganisms suspended or dissolved in water by ultraviolet radiation. In order to ensure as complete a kill as is required the time of exposure of the microorganisms should be able to be controlled in a simple manner.
It is an object of this invention to go some way towards achieving this desideratum or at least to offer the public a useful choice.